Upgrade adj_diff to handle lambda-like input providers

[bartgol]

Motivation

I wanted to use adj_diff inside EAMxx's column ops structure (specifically, the compute_midpoint_delta_impl function). But that function has to be callable when the input is not a view, but a lambda. This required an upgrade of adj_diff.

The new interface has an additional argument, which states the last valid index for which we can call v(k). That's b/c if v is a lambda, we cannot call v.size(), like we did for views.

The old interface for the case where the input is a view is still available, and simply calls the new one with index_last = v.size()-1.

Testing

Upgraded the adj_diff test to test both view and lambda providers

Separate thought: maybe adj_diff belongs to the ekat::Algorithm package?

[jgfouca]

lgtm